1. Field of the Invention
The present invention relates to a liquid storage container for storing liquid in a liquid storage chamber and a liquid ejection apparatus having the liquid storage container mounted thereon and, in particular, to a liquid storage container and a liquid ejection apparatus in which air is filled into a liquid storage chamber if a negative pressure in the liquid storage chamber exceeds a predetermined level.
2. Description of the Related Art
Some ink jet printing apparatuses have an ink storage container mounted on a carriage and supply ink stored in the ink storage container into a print head. In some ink storage containers, a negative pressure is formed inside the ink storage container to avoid leakage of ink supplied to the print head from ejection ports.
In some of the ink storage containers in which a negative pressure is formed, for example, a bag member formed by a flexible film is provided inside, and the inside or the outside of the bag member is provided with a spring or the like that urges the film in a direction in which a volume of the bag member expands. In the ink storage container having the above configuration for keeping the inside of the bag member to be a negative pressure, as the ink in the ink storage container is consumed, an absolute value of the negative pressure in the bag member gradually increases.
In general, a negative pressure is expressed as a minus value, whereas a capillary force is expressed as a plus value. To simply express a balance between the negative pressure and the capillary force, no distinction is made between a positive value and a negative value, and the term “absolute value” is used in the present specification.
Japanese Patent Laid-Open No. 2011-206936 and U.S. Pat. No. 7,703,903 disclose an ink storage container provided with a filter which allows air to be supplied to a bag member if a negative pressure in the bag member exceeds a predetermined level, so as to keep the negative pressure inside the bag member at a predetermined level in the ink storage container. Since air is introduced from the outside to the inside of the bag member through the filter if the negative pressure in the bag member exceeds a predetermined level, the negative pressure in the bag member will not increase excessively, allowing the negative pressure in the bag member to be kept at the predetermined level.
It is required that the filter which allows air to be supplied to the bag member if the negative pressure in the bag member exceeds a predetermined level be immersed in a liquid.